The present invention relates to an RFID (Radio Frequency Identification) tag that transmits information such as ID (Identification) information recorded on an IC chip at an RF (Radio Frequency).
An RFID tag consists of an IC chip and a tag antenna and is capable of transmitting information such as ID recorded on the IC chip through the tag antenna via a radio frequency (RF). Accordingly, by passing the RFID tag near a reader/writer, information recorded on the IC chip can be read in a noncontact manner at a relatively long communication distance (for example approximately 140 mm). Therefore, RFID tags are often used for production management and logistics management of products fabricated at factories. However, the communication distance significantly decreases when the RFID tag is attached directly to the surface of a metal material. To solve the problem, if a half-wave dipole antenna having a total length of a half-wave (λ/2) is used as the tag antenna of an RFID tag, the RFID tag is attached to the surface of a metal material through a spacer made of an insulator having a thickness of approximately 1 mm or more to attain a desired communication distance. Another technique has been disclosed in which a relatively thick (for example 1 mm or more thick) insulator such as a resin having a low dielectric constant or soft magnetic material is placed between the tag antenna and the attaching surface of a metal material, thereby reducing the influence of the metal material on the tag antenna to prevent reduction of the communication distance (see JP-A-2005-309811, paragraphs 0023 through 0029 and FIGS. 1 and 2, for example).